SINGAPORE (Reuters) - Noble Group’s (NOBG.SI) $3.5 billion debt rescue plan was thrown into doubt on Thursday when Singapore authorities said they would block the re-listing of shares in what was once Asia’s top commodity trader.

Singapore regulators took the decision after reviewing the findings so far of a probe into Singapore-listed Noble by Singapore police, the Monetary Authority of Singapore (MAS) and the Accounting and Corporate Regulatory Authority (ACRA).

MAS, the city-state’s central bank, and Singapore Exchange regulators concluded that “there are significant uncertainties about the financial position of New Noble”, they said in a statement, referring to the restructured unit.

“It would be imprudent to allow the re-listing as investors will not be able to trade in New Noble’s shares on an informed basis. MAS and SGX Regco (Singapore Exchange Regulation) will therefore not allow the re-listing of New Noble to proceed,” the statement said.

Noble has seen its market value all but wiped out from $6 billion over the past four years after its accounting was questioned by Iceberg Research in February 2015.

To save itself, Noble has sold billions of dollars of assets, taken hefty writedowns and cut hundreds of jobs, while defending its accounting.

The company, whose shares were suspended from trading last month due to the restructuring, wants to transform itself into an Asia-focused coal-trading business. Noble was looking to list the overhauled business as part of the restructuring, which is subject to regulatory approval,

Noble said it intended to “take steps to preserve value for stakeholders, including through implementation of the restructuring by an alternative process”. It added that it had consulted with its group of creditors.

The company said it planned to shortly provide a comprehensive response to ACRA, regarding the regulator’s investigation into the company’s technical accounting.

Amid the regulatory probe, Noble had pushed back last month’s deadline to complete its debt restructuring deal to Dec. 11 and said it was cooperating fully with authorities.

At the time of the last extension, Noble had said it had made good progress towards completing the restructuring but the timeline was delayed “due to the additional time required to fully address all concerns of the regulators”.

On Thursday, Singapore authorities said that after the investigation started, Noble had submitted financial statements which would have cut the restructured unit’s net asset value by as much as 45 percent after taking into account potential non-compliance with accounting standards.

Under the proposed debt-for-equity deal, Noble’s debt would be halved and it would get access to $800 million in trade finance and hedging facilities, a lifeline in a sector where profit margins are in the low single digits.

In return, Noble’s creditors, mostly made up of hedge funds, would own 70 percent of the restructured business, while existing shareholders’ equity would be reduced to 20 percent and Noble’s management was to get 10 percent.

Reporting by Anshuman Daga; Additional reporting by Jack Kim in Singapore and Nikhil Subba in Bangalore; Editing by Tom Hogue and Adrian Croft